Admittedly Cham has a slower older cpu. But he says he does not experience the drops in other standard competition maps. If it makes you feel any better, Poland is completely unplayable for him (insane fps drops).

Here's a quick example on how much performance boost i get when i use bumpy. I fire up ut4_Antic under vanilla and my FPS drops from a max of 105 to as low as 35. Under bumpy it drops to 120 in few areas, that alone tells me how much of a performance boost new pipeline is.

I think there is an issue in the map, a small one actually that does not affect the playability at all.As a matter of fact, rather than a bug, I would call it a eye-candy lack: near red flag, where theinflatable castle is, there is a shooting game, but the figures to be shot are only some black rectanglesof different width.